Support dict in user configuration

Depends https://gitlab.com/arkindex/backend/-/issues/1046
Refs https://gitlab.com/arkindex/requests/-/issues/679

A user should be able to configure a dict for a worker.

The display should be a table with two columns, one for key, one for values.

Each cell would have a text input that allows a user to specify strings (no need to support multiple types or casts in the frontend for now).